1. Field of the Invention
This invention relates to a liquid crystal display including a cell consisting of front and rear plane-parallel plates provided with electrode films on their inner surfaces, wherein at least the film on the front plate is transparent and segmented, and a liquid crystal of positive dielectric anisotropy is disposed inside the cell, the molecules of which exhibit preferred directions at the two inner surfaces of the cell plates, which directions are rotated by about 90.degree. to one another, and wherein a polarizer is provided at the front but not the rear plate and a reflector is provided at the rear cell plate .
2. Description of the Prior Art
Such a liquid crystal display is known from DE-OS No. 24 22 509. There a display is described in which--in contrast to the usual twisted neumatic display--only one polarizer is needed. According to DE-OS No. 24 22 509 this is made possible by the use of obliquely incident light, which must reach the reflector via selected zones of the liquid crystal layer. The contrast is effected only by those rays which, on the one hand, reach the reflector through zones of the liquid crystal layer not lying between electrodes and, on the other hand, are reflected through zones bounded on both sides by electrodes. With this method a contrast can be produced only at the edges of the individual segments of the electrode patterns. Therefore the electrode patterns must be divided into a multiplicity of small interconnected electrode stripes in order to increase the number of edges. This, however, raises the photolithographic cost in manufacture and reduces the readability of the display.
Another attempt to eliminate the second polarizer in twisted neumatic displays is known from DE-OS No. 24 32 601. In this publication there is used for this purpose a polarizing reflector which, however, is made up of a quater-wave plate, an additionally required cholesteric liquid crystal layer and an absorption layer. But by these many additionally required elements the production cost is significantly increased.
Finally there is also known from DE-OS No. 24 32 601 a twisted nematic display not having a rear polarizer. Together with a quarter-wave plate needed as an additional element, this approach calls for a departure from the 90.degree. twist of the cell to one of only 45.degree.. Apart from the fact that here again no element can be dispensed with, the 45.degree. twist generally has in the finished cell a weaker contrast between the on and off states as a consequence.